<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            height: 400px;
            width: 400px;
            background-color: yellow;
            /*text-align: center;  行居中*/
            /*line-height: 400px;  文字居中*/
            /*!*letter-spacing: 10px;*! 字符之间的距离*/
            /*word-spacing: 20px; 单词之间的距离(英语中)*/
            /*text-transform: capitalize; 首字母大写*/

        }
    </style>
</head>
<body>
    <div>hello world</div>
</body>
</html>